The classic finite difference approach is widely used, which is limited by ambiguity of diffusion coefficient between the grids or pores.

而传统的差分方法比较实用，却难以给出对分形介质网格之间的扩散系数。

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First, the partial differential equations are transformed into discrete space, discrete time nonlinear difference equations through characteristic method and finite difference approach.

首先，通过特征线法和有限差分法得到了时间离散和空间离散的非线性状态方程。

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The solution method is based on a finite difference approach, for which we present convergence characteristics. A multi-smoothing scheme is proposed to improve the convergence of the matching process.

本文采用新的弹性约束项，得到的优化方程不但容易计算而且有明确的物理意义，本文讨论了用有限差分法解这个方程的方法，对于复杂形状的轮廓匹配可以用多尺度法来解决。

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